Fungi and H. Ruth Ashbee & E. Glyn V. Evans

Diseases of the Fungi are found on virtually all body surfaces skin, , nails and ●but mainly on the skin and scalp. They are mucous membranes there either as commensals, transient flora or as are the most the cause of disease. The commensal organisms are usually , whereas the pathogens are a mixture of common of fungal moulds and yeasts. , with treatment costing ● Fungi and healthy skin millions of pounds The only fungi to live permanently on the skin as each year in the UK. commensals belong to the genus . Malassezia species are dimorphic and most of the species in the genus have an absolute requirement for lipid to enable them to grow. Their lipophilic nature is responsible for defining the areas on the body where Malassezia occurs – namely those areas rich in sebaceous glands, such as the face, scalp, chest and back. The genus has recently been re-organized on the basis of molecular taxonomic studies and now includes six lipophilic species: M. furfur, M. sympodialis, M. globosa, M. obtusa, M. restricta and M. slooffiae. There is also a seventh which affects the keratin member of the genus, M. pachydermatis, that does not in hair, nails and stratum require lipid for growth and is usually not found on corneum (top layer) of the , but is often found associated with animals. skin. About 20 species of BELOW: Population densities of Malassezia vary from person to fungi from Fig. 1. Body ringworm caused by person, as well as from site to site. However, on the chest the genera , ( 4 –2 ringworm). and back as many as 10 organisms cm have been Microsporum and Epidermo- COURTESY E.G.V. EVANS recorded, whilst on the hands and feet there may be as few phyton are responsible. Most as <4 organisms cm–2. The age at which colonization infections are caused by a TOP RIGHT: occurs is controversial, with some workers reporting it in single species, Trichophyton Fig. 2. lesion on the scalp children of only a few weeks of age and others finding no rubrum. Ringworms also due to . colonization until puberty. What is known is that occur in animals and these COURTESY E.G.V. EVANS maximal population densities occur in adults between may spread to humans; late teens and early middle age, after which the number transfer is commonest with LOWER RIGHT: of organisms decreases as people get older. Microsporum canis, the cause Fig. 3. due to Candida is found on the skin of some individuals, but of ringworm in cats and . it is not a true commensal and carriage is usually dogs. COURTESY DR DAI ROBERTS, SOUTHERN GENERAL HOSPITAL, transient. The species found include and Ringworm lesions vary considerably in appearance, GLASGOW Candida parapsilosis. Candida may also be present on the according to the site of the infection and the species of mucous membranes of the mouth and vagina but here involved. Sometimes there is only dry scaling or it does occur as a commensal. The percentage of hyperkeratosis, but more commonly there is irritation, people colonized and the level of colonization varies , swelling and vesicles. More inflammatory considerably between different groups in the population lesions with weeping vesicles, pustules and ulceration are but around 10–20 % of healthy individuals are thought usually caused by animal ringworm. The spreading, to carry commensal Candida. ring-like lesions with a raised, inflammatory border Both Malassezia and Candida are able to cause disease from which the disease name derives are seen on the under certain circumstances. body, face and scalp (Fig. 1). In infections of the scalp there is scaling and and sometimes a severe ● Fungi and skin disease inflammatory response resulting in a raised boggy lesion Diseases of the skin, hair, nail and mucous membranes called a kerion (Fig. 2) – this needs to be diagnosed and are the most common of all fungal infections and they treated promptly otherwise there may be permanent have a worldwide distribution. hair loss. In nail infection, the nail becomes discoloured, thickened, raised and crumbly (Fig. 3). Ringworm: Most of these infections are caused by a Ringworm is the only truly contagious fungal group of keratinophilic moulds known collectively as infection and spreads through direct or indirect contact . They cause a complex of diseases, with an infected individual or animal. The infective collectively known as ringworm (clinical name Tinea), particle is usually a fragment of keratin containing

132 MICROBIOLOGYTODAY VOL 27/AUG 00 These now comprise about 75 % of all ringworm TOP LEFT: infections diagnosed in temperate zones. It is estimated Fig. 4. Ringworm of the that around 10–15 % of the general population in the clefts (Athlete’s foot) due to Trichophyton rubrum. UK has foot ringworm and 5 % . Currently, COURTESY DR DAI ROBERTS, nothing is done to control the spread of these infections SOUTHERN GENERAL HOSPITAL, despite the fact that vast sums are spent treating them. GLASGOW The disinfectant foot-bath in swimming pools is worse than useless for controlling foot ringworm and is likely MIDDLE LEFT: Fig. 5. Candida albicans to contain a soup of skin scales, many of which contain infection of hand (interdigital fungus – jump over it! space). Although dermatophytes are essentially disease- COURTESY E.G.V. EVANS causing organisms, some believe in a carrier status. Dermatophytes can be isolated, for example, from the LOWER LEFT: feet or scalp without there being any obvious sign of Fig. 6. Candida infection of the nail fold (). infection. Others dispute this and say that if you look COURTESY E.G.V. EVANS hard enough you will find lesions.

Yeast infections: Infections due to Candida and Malassezia are generally endogenous in origin. Candida can cause infections at many sites on the body, commonly the folds, such as the armpits or beneath the breasts, where there is occlusion and increased moisture. The lesions appear as well demarcated, inflamed areas that may itch. The nappy area in babies, the groin and the skin between fingers (Fig. 5) and may also be affected. Candida may also cause paronychia – inflammation around the cuticle of the nail, which may lead to swelling and production of (Fig. 6). It is common in kitchen workers and other people who frequently have their hands in water. Candida infection of the mouth and vagina is generally known as thrush because of the presence of white plaques of yeast on the surface of the mucous membrane (Fig. 7). Vaginal candidosis is very common and most women develop an infection at some point, frequently during pregnancy, and some suffer from recurrent infections. Oral infections are seen mainly in babies and the elderly. A number of predisposing factors are recognized for Candida infection, especially antibiotic therapy and immuno- suppression, either - or disease-induced. For example, intractable chronic oropharyngeal candidosis is common in AIDS patients (<100 %) and frequently viable fungus. Indirect transfer may occur via the there is associated oesophageal infection. The appearance floors of swimming pools and showers or on brushes, of this infection often indicates the transition from combs, towels and animal grooming implements. In HIV-positive to full-blown AIDS. industrialized countries, ringworm of the scalp, which Malassezia is able to cause several skin conditions, occurs almost exclusively in children before puberty, including pityriasis versicolor, seborrhoeic dermatitis accounts for only a small proportion of infection and is and . It has also been known to cause mostly caused by dermatophytes of animal origin, systemic infection, including catheter related fungaemia although scalp infections due to the human species, in suitably predisposed individuals, such as newborn , are on the increase in Europe. infants fed intravenously with high lipid feeds. Foot ringworm (athlete’s foot; Fig. 4), with its associated Pityriasis versicolor takes the form of scaly hypo- nail and groin infections is the commonest fungal or hyper-pigmented lesions (Fig. 8) with minimal disease and the increased use and availability of inflammation or itching. It occurs on the upper trunk, communal bathing facilities have brought this about. but may spread to include upper arms, legs and buttocks

MICROBIOLOGYTODAYVOL 27/AUG 00 133 itraconazole and flucon- azole, although is the most potent anti- dermatophyte drug. Candida infections and pityriasis versicolor respond well to the application of topical agents, although oral and itra- conazole are alternatives for severe or extensive cases. With pityriasis versicolor relapse is a major problem (reaching 60 % within 1 year). Topical , in extensive cases. In pity- along with topical steroids, may also be used for riasis lesions, both the yeast treatment of seborrhoeic dermatitis. and mycelial forms of Malassezia are present and ● Future prospects diagnosis is usually made Current research into superficial fungal infections is on the basis of clinical focussing, for example, on molecular typing of dermato- presentation and the char- phyte strains to answer questions on epidemiology acteristic appearance of and pathogenesis; questions such as whether or not ‘spaghetti and meat-balls’ particular strains of dermatophyte species are more likely on microscopical exam- to cause nail (as opposed to skin) disease than others. ination of skin scrapings. There is an unaddressed need to develop measures to Among the predisposing control foot and nail infections in communal bathing factors for pityriasis, high places. This would help reduce the expenditure on the TOP & LOWER LEFT: temperature and humidity appear to be the most treatment of these infections, especially as currently Fig. 7. Candida infection of the important. In hot climates it is often the most common in the UK this costs circa £45.5 million. mouth showing white yeast plaques fungal infection seen. Current treatments for superficial mycoses are (top) and severe mouth infection in Seborrhoeic dermatitis presents as scaly lesions on generally satisfactory, although there is scope for an AIDS patient (bottom). COURTESY E.G.V. EVANS the face, upper trunk and scalp which itch and are improvement, particularly in nail disease where about inflamed. Around 1–3 % of the normal population are 20 % of patients fail treatment. A number of new UPPER RIGHT: affected, but in HIV-positive patients the prevalence agents, mainly azoles and cell wall inhibitors, Fig. 8. Pityriasis versicolor may be as high as 80 %. Predisposing factors are are likely to become available over the next 1–3 years. of skin with hyper pigmentation. not well characterized, but stress may be important. Initially, it is probable that they will be used to treat COURTESY E.G.V. EVANS The condition is chronic and relapses are frequent. systemic fungal infections but may be used later for Diagnosis is largely based on clinical presentation. superficial mycoses. consists of itchy -like spots and pustules on the trunk and upper arms. ● Dr H. Ruth Ashbee is a Clinical Scientist and Antibiotic administration is the main predisposing Honorary Lecturer, Mycology Reference Centre, factor, particularly in the immunocompromised, but Division of Microbiology, University of Leeds and overgrowth of Malassezia may be secondary to occlusion General Infirmary, Leeds, LS2 9JT. of the follicles. Tel. 0113 233 5598; Fax 0113 233 5640; email [email protected] Diagnosis: Ringworm and Candida infections may be ● E. Glyn V. Evans is Professor of Medical reliably diagnosed in the laboratory by microscopical Mycology and Director, Mycology Reference examination and culture of skin, hair, nail or material Centre, Division of Microbiology, University of from mucous membranes. Leeds and General Infirmary, Leeds, LS2 9JT. Tel. 0113 233 5600; Fax 0113 233 5587; Treatment: Ringworm generally responds well to email [email protected] topical creams, etc., except for nail and scalp infections, which require oral therapy. Topical agents include a number of azoles and terbinafine and amorolfine. Oral therapies include terbinafine and the triazoles

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